As per the question, Charge is moving in y-direction. Electric field and magenetic fields are in x-direction. magnetic field does not accelerate the
charged body since its direction of motion is perpendicular to direction of movement of charged body. Only electric field can give accelerated motion to the charge and change its velocity.
Acceleration due to electric field = (qE)/m .
If we apply the standard equationof motion " v = u+at ", the relation involving initial velocity v0, final velocity 2V0, acceleration and time is given by
2 v0 = v0 + (qE/m) × t
then we get t = ( mv0) / ( qE )
but this is not given in the options